Attachment_2_Grant_Grove_NTCRAWP-Final.pdf

Prepared for:

NATIONAL PARK SERVICE

Pacific West Regional Office

333 Bush Street, Suite 500

San Francisco, California 94104

Non-Time Critical Removal Action Work Plan

For

Grant Grove Burn Dumpsite Solid Waste Management Unit No. 38

Sequoia and Kings Canyon National Parks

Fresno County, California

September 2023

Prepared By:

Grant Grove Burn Dumpsite, Removal Action Plan September 2023 ii

SIGNATORIES:

Holly A. Trejo / Principal Geologist

Environmental Professional’s Name/Title

Signature

September 7, 2023 Date

By signing above, I attest that I meet the qualifications of an Environmental Professional as defined under

40 CFR §312.10(b) and that this document was prepared by me or under my supervision/responsible charge.

Professional Engineer/Geologist Seal

Ratified by:

Environmental Compliance and Cleanup Division

Signature Date i

Table of Contents

Acronyms and Abbreviations ....................................................................................................... iii

1 Introduction

2 Purpose

3 Site Condition and Background

3.1 Site Location and Description

3.2 Operational History

3.3 Physical and Environmental Setting

3.3.1 Site Hydrogeologic Setting and Sensitive Ecosystems

3.3.2 Type, Source, and Location of Known Contamination

3.3.3 Previous Site Investigations

3.3.4 Summary of EE/CA Results

3.3.5 EE/CA Risk Assessment Summary

3.3.6 Site Visit

3.3.7 Regulatory Framework

3.3.8 Removal Action Objectives

3.3.9 ARARs

4 Selected Removal Alternative

5 Removal Action Implementation

5.1 Site Visit and Coordination

5.2 Waste Characterization and Disposal Plan

5.2.1 Extent of Contamination Sampling

5.2.2 Excavation Plan

5.2.3 Excavation Extent and Confirmation Sampling

5.2.4 Waste Characterization of Stockpile

5.2.5 Waste Manifest, Transportation, and Disposal Plan

5.2.6 Backfill and Site Restoration

5.3 Site Control Plan

5.4 Cultural Resources Control Plan

6 Erosion Control Plan

6.1 Potential Pollutant Sources

6.2 Stormwater and Sediment Control

6.2.1 BMPs for Preconstruction Erosion Control

6.2.2 BMPs for Water Erosion

6.2.3 BMPs for Wind Erosion

6.2.4 BMPs for Tracking Sediment

6.2.5 BMPs for Construction Vehicle and Equipment Spills

6.2.6 Inspection, Maintenance, Repair, and Reporting

6.2.7 Hazardous Material Spill Plan

7 Traffic Control Plan ii

7.1 General Approach

7.1.1 Construction Signs

7.1.2 Traffic Controls

7.1.3 Onsite Traffic

7.1.4 Offsite Traffic

8 Reporting

9 Schedule

10 References

FIGURES

Figure 1: Regional Site Location Map Figure 2: SI and EECA Soil Sample Locations Figure 3: Site Plan Figure 4: Traffic Control Plan Map Figure 5: Geophysical Survey Line Locations Figure 6: Summary of Ecological-PRG Soil Sample Detection and Exceedances Figure 7: COC Impact Area

APPENDICES

Appendix A: ARARs from 2018 Avatar EE/CA iii

ACRONYMS AND ABBREVIATIONS

95% UCL 95% Upper Confidence Limit on the Arithmetic Mean

AGS Advanced Geological Services amsl Above Mean Sea Level

ARAR Applicable or Relevant and Appropriate Regulations

Avatar Avatar Environmental, LLC

BMP Best Management Practice

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CFR Code of Federal Regulations

COEC Constituents of ecological concern cy Cubic Yards

DTSC Department of Toxic Substance Control

DU Decision Unit

ECM ECM Consultants

EE/CA Engineering Evaluation/Cost Analysis

EM Electromagnetic

EPA U.S. Environmental Protection Agency

FHWA Federal Highway Administration

GPR Ground Penetrating Radar

GPS Global Positioning System

HAZWOPER Hazardous Waste Operations and Emergency Response

HH Human Health

HHRA Human Health Risk Assessment

IDW Investigation-derived waste

ISM Incremental Sampling Methodology

ITRC Interstate Technology & Regulatory Council

LOAEL Lowest observed adverse effect level mg/kg milligrams per kilogram mg/L milligrams per liter

MUTCD Manual on Uniform Traffic Control Devices

NOAEL No observed adverse effect level

NPS U.S. Department of the Interior, National Park Service

O&M Operation and Maintenance

PA Preliminary Assessment

PAH Polyaromatic Hydrocarbons

PRG Preliminary Remedial Goals

RAA Removal Action Alternative

RACR Removal Action Completion Report

RAO Remedial Action Objectives

NPS National Parks Service iv

NTCRAWP Non-Time Critical Removal Action Work Plan

RA Risk Assessment

RG Remediation Goal

SEKI Sequoia and Kings Canyon National Parks

SL Seismic Line

STLC Soluble Threshold Limit Concentration

SWMU solid waste management unit

SWPPP Stormwater Pollution Prevention Plan

TCLP Toxicity Characteristic Leaching Procedure

TPH Total Petroleum Hydrocarbons

TPZ Tree Protection Zone

TRV Toxicity Reference Values

TSD Transport, Storage, and Disposal

TTLC Total Threshold Limit Concentration

WET California Title 22 Wet Extract Test

XRF X-ray fluorescence

1 INTRODUCTION

ECM Consultants (ECM) prepared this Non-Time Critical Removal Action Work Plan (NTCRAWP) for the U.S. Department of the Interior, National Park Service (NPS) to perform excavation and analysis of contaminated soils at the Grant Grove Burn Dumpsite Solid Waste Management Unit (SWMU) No. 38 (Site) located within the Sequoia and Kings Canyon National Parks (SEKI) in Fresno County, California (Figure 1). The removal action will be performed in accordance with the Action Memorandum (NPS, 2018) decision document. NPS is conducting the response action as lead agency under their delegated Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) authority. This NTCRAWP describes the objectives, procedures, and scope of work for the Grant Grove Removal Action.

2 PURPOSE

The purpose of this NTCRAWP is to direct the execution of the removal action at the Site based on the remedial alternative selected in the Final EE/CA Approval Memorandum (NPS, 2018) and the Engineering Evaluation/Cost Analysis (EE/CA [Avatar, 2018]). The recommended alternative includes excavation of contaminated soils that exceed cleanup goals and disposal at an off-site facility. The purpose of the removal action is to meet the remediation goals defined in the EE/CA and the Action Memorandum.

The Action Memorandum (NPS, 2018) indicates that the results of the human health risk assessment (HHRA) show that present conditions at the site would not result in an unacceptable risk to reasonably anticipated current and/or future human health receptors.

Based on Site cancer risks well below the target cancer risk goal of IE-06 and noncancer and His well below the noncancer threshold of 1, contaminants of concern (COCs) were not identified and therefore remediation goals (RGs) were not calculated for the HHRA.

However, the ecological risk assessment (RA) documents potential exposure and risks to ecological receptors exposed to soil contamination within the Site, specific receptors include terrestrial plants, soil invertebrates, mammals and birds. Remediation goals are detailed in the Action Memorandum (NPS, 2018) using both no observed adverse effect level (NOAEL)-based and lowest observed adverse effect level (LOAEL)-based toxicity reference values (TRVs).

3 SITE CONDITION AND BACKGROUND

3.1 Site Location and Description

The Site is located within SEKI in Fresno County, California. The Site is approximately 1 mile north-northwest of the community of Wilsonia and 0.46 miles north-northwest Grant Grove Village, west of Generals Highway and northeast of the horseback riding facility. The Site is located at 36°44'46.97" north (latitude) and -118°58’1.46” west (longitude) at an elevation of approximately 6,620 feet above mean sea level (amsl). The general location of the Site is shown in Figure 1.

The Site is located on a west-facing hillside bordered by a horse trail, as shown on Figure 2.

There are three primary drainages that extend from the Site perimeter downslope to the northwest and to the southwest as shown by the seismic lines SL-1 (north-northwest), SL-2 (south-southwest), and SL-3 (west-northwest) on Figures 3 and 4.

Access to the Site is via a gated, unpaved, road on the west side of Highway 180, 3.5 miles from the SEKI Grant Grove Big Stump Entrance Station, approximately 0.25 miles north of Wilsonia and the Grant Grove Visitor Center. The unpaved site access road from Highway 180 veers north and reaches the Site after 0.11 miles as shown in Figure 5.

The refuse accumulation area is where waste and ash are buried and covered by a veneer of soil pushed on top of the refuse. The debris field consists of the approximate area where dump-related debris is found strewn across the ground surface but is not believed to have a depth greater than 6 to 12 inches. Together, these impact areas are estimated to have an area of 2.24 acres and a volume of 7,400 cy. The estimated extent of excavation during removal action and supporting sample results from the EE/CA are shown by on Figures 4, 6, and 7.

There are several stockpiles of construction materials currently onsite. These construction materials consist of base rock, large boulders, asphalt for recycling, asphalt cold patch, soil fill material, and wood chips. Materials associated with the waste dump exist along the perimeter of the Site and on the downslope sides of the waste dump. The waste material consists of rusty metal, glass bottles, broken ceramic containers, batteries, and some plastic debris. The SWMU #38 waste material is currently uncontained and covered with minimal soil or partially exposed.

3.2 Operational History

Sequoia National Park was established in 1890 to protect the General Grant Grove of giant sequoias. Sequoia National Park connects with Kings Canyon National Park and have been administered together by the NPS since 1943.

The Grant Grove Burn Dumpsite SWMU No. 38 was used as a domestic waste burn pit from 1929 to 1965. The former incinerator at Grant Grove SWMU # 38 was built in the 1960s but was never used as a waste incinerator. Records indicate that it was dismantled in 1975. The Site was used for several decades (36 years) as a burn and burial pit for domestic waste and is currently being used by the NPS as a staging area for construction materials and wood chips.

3.3 Physical and Environmental Setting

3.3.1 Site Hydrogeologic Setting and Sensitive Ecosystems

SEKI is located on the western side of the Sierra Nevada Mountain range, which is characterized by primarily igneous rock formations. Metamorphic limestones and marbles are also common within SEKI. Soils in this area derived from igneous and metamorphic rock are generally granular and thin. A significant amount of the Sierra Nevada Range is contained within SEKI as well as parts of the Great Western Divide.

SEKI contains approximately 3,200 lakes and ponds and approximately 2,600 miles of rivers and streams. The waters originate at elevations between 8,900 to 12,100 feet. These streams flow through meadows and join larger streams and rivers. The main river systems in SEKI are the south Fork of the San Joaquin, the North Fork of the Kern, the South and Middle Forks of the Kings, and the five forks of the Kaweah.

There are three primary drainages that extend from the Site perimeter downslope to the northwest and to the southwest as shown by the seismic lines SL-1 (north-northwest), SL-2 (south-southwest), and SL-3 (west-northwest) on Figures 3 and 4.

Groundwater depth ranges from 10 to 250 feet below ground surface and is assumed to generally follow topography, flowing northwest from the Site toward the Central Valley. There is one water production well upstream from the Site and 39 upgradient groundwater wells have been installed in the town of Wilsonia. One water spigot was observed near the northwestern portion of the Site.

3.3.2 Type, Source, and Location of Known Contamination

Generally, contaminants may be released by mechanisms such as storm water runoff, wind erosion of surface soil, leaching and infiltration to the subsurface, migration through the subsurface soil to the water table, and ground disturbance within areas of contamination. Once released from the source, contaminants can be present in groundwater, air, surface water, or sediment.

The presence of elevated contaminant concentrations has been confirmed by soil sampling and analysis during the Engineering Evaluation/Cost Analysis (EE/CA [Avatar, 2018]). Contaminants have been detected in surface and near-surface soils. It was also noted that contaminants are migrating down-gradient from the former burn pit within the dry stream channel drainages.

Figure 6 (Avatar, 2018, Figure 16) provides a graphical representation of the detected concentrations and their exceedances of the ecological PRGs. As shown, sample locations GG- SO-05 and GGSO-06 have the highest number of exceedances with six RG exceedances.

Sample location GG-SO-08 had two exceedances and GG-SO-07 had one exceedance.

Drainage samples GGSO-01 through GG-SO-04 did not have any PRG exceedances.

The area of COC impact can be divided into a refuse accumulation area and an adjoining debris field, as shown in Figure 7 (Avatar, 2018, Figure 17). The refuse accumulation area is where waste and ash are buried and covered by a veneer of soil pushed on top of the refuse. The debris field consists of the approximate area where dump-related debris is found strewn across the ground surface but is not believed to have a depth greater than 6 to 12 inches. Together, these impact areas are estimated to have an area of 2.24 acres and a volume of 7,400 cy.

Dry soil in all three of the drainages shown on Figure 3 (extending from the Site perimeter downslope to the northwest and to the southwest as shown by the seismic lines SL-1 , SL-2, and SL-3) has concentrations of metals and total petroleum hydrocarbons (TPHs), while the dioxin/furan concentrations were limited to the central and south drainages only. However, soil in these drainages is considered an incomplete pathway for human and ecological receptors as detailed in the EE/CA and thus is not part of this removal action. The risk from ephemeral surface water and underlying groundwater is not considered likely due to the Site’s location in relation to existing water bodies. Risk considerations for ephemeral surface water and groundwater have been excluded from the scope of the removal action (SEKI, 2018). Direct exposure to contaminated soil is the primary exposure pathway for human and ecological receptors.

As described in the EE/CA, soil samples were collected throughout the Site at each Decision Unit (DU).

3.3.3 Previous Site Investigations

Assessment Reports

In March 2013, the California Department of Toxic Substances Control (DTSC) completed an Assessment Report (DTSC, 2013) that included six SWMUs in SEKI. The DTSC Assessment Report concluded that further environmental investigation was needed at SWMU No. 38 to determine the nature and extent of any release of hazardous waste or hazardous waste constituents from the Site. The DTSC Assessment Report also documented a Site visit conducted by DTSC and the NPS staff at SWMU No. 38 on October 18, 2012. Observed waste material around the downslope perimeter of the Site consisted of ash debris, bottles, ceramic plates, broken glass, and metal. Although NPS indicated that the area was partially excavated and backfilled with clean fill during dismantling of the incinerator, waste material remains in place. The DTSC Assessment Report stated: “this area is considered a potential environmental concern and further investigation is warranted.”

Preliminary Assessment

In November 2013, a Preliminary Assessment (PA) that included SWMU No. 38 was conducted (ECM, 2014). The scope of the investigation included a review of available local, state, and federal agency file information; a preliminary evaluation of potential impacts to Site media; an identification of potential migration routes, exposure pathways, and receptors; a Site reconnaissance; and interviews with the NPS personnel. The results of the PA indicated that complete pathways of potential contaminant exposure to human and ecological receptors exist for soil, sediment, and surface water in the vicinity of the Site.

Site Inspection

A Site Inspection (SI) performed in June 2015 (ECM, 2015) quantified the concentrations of COPCs in the waste material, assessed potential impacts to the surface soil adjacent to the waste material, and assessed dry soils downgradient from the Site. Soil samples upgradient of the Site were collected using an Incremental Sampling Methodology (ISM) to obtain background concentrations of metals in native surface soil near to the Site. The Site and background sampling locations for the SI investigation are presented on Figure 2 of the Site Inspection Report SEKI – Grant Grove SWMU #38. The SI Report recommended the preparation of an EE/CA for the selection of a removal action alternative for the Site. The SI identified 12 heavy metals (antimony, arsenic, barium, cadmium, chromium, cobalt, copper, lead, mercury, thallium, and zinc), TPH (diesel and oil range), 9 polyaromatic hydrocarbons (PAHs), 16 dioxins, and 10 herbicides and pesticides at the Site.

3.3.4 Summary of EE/CA Results

The EE/CA report was prepared in July 2018 by Avatar Environmental, LLC (Avatar) to summarize the field sampling activities conducted in 2016 and 2017, conduct a risk assessment, and recommend a removal action alternative (RAA) based on the results.

The background sampling location for the SI and EE/CA investigation is shown on Figure 2 and Site features are illustrated in Figure 3. Additional field investigation sampling was conducted as part of the EE/CA process in 2016 and 2017 to quantify the area and depth of waste dump material and adjacent impacted soil, as well as to conduct background soil sampling.

The refuse area was characterized by composited samples comprising subsamples of visually homogenous layers having a volume of less than 1,000 cy. The debris area was characterized via samples composited from subsamples within an area of less than one acre. Both areas were sampled for 17 metals, TPH, PAHs, pesticides and herbicides, and dioxins/furans.

The maximum Site soil concentrations exceeded background threshold values (BTVs), and both human health and ecological screening levels were exceeded for several contaminants. The BTVs were based on 15 discrete background soil sample results collected during the EE/CA and were derived by calculating the 95% Upper Simultaneous Limits (USLs) based on left-censored data with multiple detection limits as recommended in the USEPA ProUCL Technical Guidance Manual (Avatar, 2018 [USEPA, 2015b]).The HHRA concluded that there were no unacceptable Site soil risks to reasonably anticipated current and/or future human health receptors. However, the ecological risk assessment results estimated that Site metals and dioxin concentrations in soil are posing an unacceptable risk to ecological receptors.

Avatar collected four subsurface waste materials samples to delimit the extent of the COPC migration within the three dry creek channel drainages which included the following:

• Northern drainage (GG-SO-01): Detected analytes included DRO, ORO, and ten metals.

• Central drainage (GG-SO-02): Detected analytes included ORO, 2 dioxin/furan congeners, and ten metals.

• Southern drainage (GG-SO-04): Detected analytes included ORO, 2 dioxin/furan congeners, and ten metals.

No semi-volatile organic compounds, pesticides, or herbicides were detected among the three drainage locations. Although potential contaminant migration to downstream drainages exists, no unacceptable human health or ecological Site risks were found for soils in the downgradient Site drainages.

To evaluate waste characterization of the in-situ refuse for off-Site disposal, two 4-point composite samples (GG-SO- 05 and GG-SO-06) and two 2-point composite samples (GG-SO- 07 and GG-SO-08) were collected representing approximately 7,400 cy of material accumulated onsite. Due to the heterogeneity present in each type of material, composite sampling was used to evaluate the general character of the refuse and debris potential waste streams.

To quantify the area and depth of waste dump material and adjacent impacted soil, Advanced Geological Services, Inc. (AGS) performed the geophysical investigation, which included seismic refraction, ground penetrating radar (GPR) and electromagnetic terrain conductivity (EM) surveys to assess the thickness and extent of buried refuse at the Site during the EE/CA.

Seismic refraction was performed to delineate an upper low-velocity layer corresponding to buried refuse. GPR was performed to assess refuse thickness by imaging the top-of-bedrock surface. EM surveying was performed to look for conductivity anomaly(ies) indicative of buried refuse.

Findings from the geophysical survey include the following:

• Buried refuse appears to occur in two lobes separated by the granitic ridge angling northwest away from the Site’s central plateau (Figure 4).

• Seismic refraction data, along with backhoe trench and hand-auger findings, indicate that refuse thickness ranges from less than one foot to greater than 10 feet.

• Because the “silty brown sand” found in backhoe trenches exhibits the same seismic velocity as buried refuse, they cannot be distinguished with seismic refraction alone.

Accordingly, AGS’s interpretation of refuse thickness and extent is based on both the seismic results and Geocon’s backhoe/hand-auger findings. The interpreted extent of buried refuse is indicated by a red dashed line on Figure 4.

• Rough estimates of refuse volume are 2,600 cubic yards (cy) for the northern lobe and 2,200 cy for the southwestern lobe, totaling 4,600 cy.

• An estimate of the volume of debris surrounding the Site refuse areas based on the area of observed surficial debris shown on Figure 7, is 2,800 cy.

3.3.5 EE/CA Risk Assessment Summary

The results of the HHRA indicate that leaving the waste material associated with the Site in its present condition would not result in an unacceptable risk to reasonably anticipated current and/or future human health receptors.

The potential ecological adverse effects indicated in the ecological RA, and resultant COECs include seven metals and one dioxin. Copper and zinc indicated potential adverse effects for all four receptors and lead indicated potential adverse effects for three receptors (terrestrial plants, avian, and mammalian). Cadmium indicated potential adverse effects for both avian and mammalian receptors, and chromium (soil invertebrates), mercury (soil invertebrates), vanadium (terrestrial plants), and 2,3,7,8-TCDD TEQ (mammalian) indicated potential adverse effects for only one receptor. Exceedances of background values and screening levels were used to calculate RGs shown in Table 1 below.

Comparison of the SI and EE/CA contamination observed in the drainages with those detected in the Former Burn Dump Area indicates that contaminants are migrating down-gradient from the Former Burn Dump Area within all three drainages. The HHRA found that neither of the drainages nor the Former Burn Dump Area pose an unacceptable risk to human health receptors. The ecological RA found that all the adverse effects to terrestrial plant and soil invertebrates are based on COEC concentrations within the Former Burn Dump Area only, which includes the refuse area and debris field (Figure 7). This same conclusion also applies to the results found as part of the SI investigation.

Furthermore, although avian and mammalian HQs were based on receptor exposure to the entire Site, all the HQs greater than 1 were a result of concentrations detected within the Former Burn Dump Area. Soil invertebrate and plant receptors were also considered in the ecological risk assessment.

Food-chain modeling-based RGs were developed using avian and mammalian receptor dietary exposure modeling with a specified target risk, solving for the medium concentration. HQs were used as a multiplier to calculate RGs as described in the EE/CA (Avatar, 2018). These RGs were developed using both NOAEL-based and LOAEL-based TRVs. Terrestrial plant and soil invertebrate RGs were derived from the LANL ECORISK Database based on the geometric mean of the NOAEL and LOAEL ESLs.

Table 1 below presents a summary of the ecological receptor specific risk-based soil RGs for each associated chemical along with final overall RGs. Cadmium, copper, vanadium, zinc, and 2,3,7,8-TCDD TEQ final overall RGs are based on the ecological risk-based soil RGs calculated in the EE/CA (Avatar, 2018).

Table 1: BTVs, Ecological RGs, and Final Overall RGs

COPEC Receptor BTVa

(mg/kg) Soil RGb

(mg/kg)

Final Receptor- Specific Soil RGc (mg/kg)

Final Overall Soil RGc (mg/kg)

Cadmium Bird

NC

2 2

1d Mammal 1 1

Chromium Soil Invertebrate 13 1.1 13 13

Copper

Plant

185 185

61d Soil Invertebrate 206 206

Bird 61 61

Mammal 79 79

Lead

Plant

262 262

53 Bird 30 53

Mammal 191 191

Mercury Soil Invertebrate 0.2 0.16 0.2 0.2

Vanadium Plant 37 69 69 69d

Zinc

Plant

360 360

175d Soil Invertebrate 334 334

Bird 175 175

Mammal 671 671

2,3,7,8-TCDD TEQ Mammal NC 0.0000036 0.0000036 0.0000036 d aBTV values based on 95% USLs.

bSoil RGs are risk-based, receptor specific, and include hazard quotient multipliers. See EE/CA (Avatar, 2018) for full RG derivations.

cFinal receptor-specific RG is the higher of the BTV or receptor-specific soil RG.

dFinal overall RG is the minimum of receptor-specific RGs.

3.3.6 Site Visit

ECM completed a Site visit accompanied by NPS personnel on October 13, 2022. ECM observed that waste material conditions at the Site were unchanged from those documented in the EE/CA. The former Burn Pit area of the Site depicted with rock piles and soil mounds in Figure 3 was largely covered by wood chips. The KNP Complex fire burned areas of SEKI in 2021 and hazard trees throughout the park have been felled, chipped, and stored on Site in place of the rock piles and soil mounds shown on the figures, which were removed prior to October 13, 2022. NPS was also conducting equipment operation training at the Site when ECM arrived for the Site visit. ECM observed several large Jeffery Pines growing within the waste material and discussed tree protection with NPS as detailed in Section 5.2.2.2. ECM and NPS also discussed cultural resource protection as detailed in Section 5.4.

3.3.7 Regulatory Framework

The NTCRAWP is being performed in accordance with CERCLA and the Applicable or Relevant and Appropriate Requirements (ARARs) described in Section 3.3.7 below and included in Appendix A.

3.3.8 Removal Action Objectives

The removal action objectives (RAOs) are based on the reported sources of contamination, the nature and extent of contamination, results of the human health and ecological risk evaluations, Site specific Removal Goals (RGs) (referred to as Preliminary Remedial Goals [PRGs] in the EE/CA) and the identified ARARs for the Site. RAOs were developed to control the contamination sources and reduce exposure of human and ecological receptors to Site contamination. The RAOs for the Site are:

1. Remove waste debris (ash, glass, ceramics, concrete, and metal) from the Site surface and subsurface based on results of the EE/CA Geophysical Survey described in Section 3.3.4, visual evidence of waste materials observed during excavation, X-ray fluorescence (XRF) screening results, and laboratory ISM confirmation results;

2. Prevent or reduce potential for ecological exposure to contaminants of ecological concern (COECs) in soil; and

3. Prevent or reduce potential migration of COECs via surface runoff, erosion, and wind dispersion.

The area of COEC impact can be divided into a refuse accumulation area and an adjoining debris field. The refuse accumulation area is where waste and ash are buried and covered by a veneer of soil pushed on top of the refuse as shown in Figures 4 and 7. The debris field consists of the approximate area where dump-related debris is found strewn across the ground surface but is not believed to have a depth greater than 6 to 12 inches. Together, these impact areas are estimated to have an area of 2.24 acres and a volume of 7,400 cy. The refuse accumulation area and debris field are illustrated on Figure 7.

3.3.9 ARARs

Consistent with CERCLA Section 121(d) and in compliance with NCP Section 300.415(j), CERCLA removal actions must, to the extent practicable considering the exigencies of the situation, attain ARARs under federal or state environmental or facility siting laws at the completion or during the implementation of the removal action, or both depending on the nature of the requirements. ARARs consist of cleanup standards, standards of control, and other substantive requirements, criteria, or limitations promulgated under federal environmental or state environmental or facility siting laws, however state ARARs are only applicable if they are more stringent than federal. See 40 C.F.R. § 300.5.

Pursuant to its delegated CERCLA lead agency authority, NPS has identified ARARs and To Be Considered for the Grant Grove Burn Dumpsite Area EE/CA. The results of the ARAR analysis, including state ARARs, are summarized in Appendix A. ARARs most applicable to this removal action are those under the Location-Specific and Action-Specific types in Appendix A. These include ARARs pertaining to delegation of authority to cleanup federal land, protection of sensitive species, protection of cultural resources, waste transport and disposal, and waste staging.

4 SELECTED REMOVAL ALTERNATIVE

Based on the analysis of Removal Action Alternatives (RAAs) in the EE/CA, excavation and disposal of contaminated soils exceeding the RGs for Site COECs is the recommended alternative defined in the Action Memorandum (NPS, 2018) as agreed upon by NPS and SEKI.

Excavation and off-Site disposal involves the removal of the contaminated materials, final classification of the waste as RCRA Subtitle C or other regulated hazardous waste, and subsequent disposal at a facility licensed to accept the waste. The type of facility is dependent on the class and concentration of hazardous materials in the waste. Wastes found to exceed State or Federal guidelines for hazardous material must be transported to a RCRA landfill for disposal. Wastes not exceeding the guidelines can be placed in any landfill licensed to accept the waste. All excavated wastes will be managed in accordance with all applicable federal, state, and local requirements. While the soil has not been characterized for disposal, the identified concentrations of lead at the Site may meet the criteria for RCRA hazardous waste since lead concentrations greater than 100 mg/kg were detected.

Total lead in soil analyzed by EPA 6010B was present at 400 mg/kg, greater than 20 times the federal hazardous waste limit of 5.0 milligrams per liter (mg/L) in composited samples collected from the debris and refuse areas. Based on this elevated concentration, these materials may exceed the RCRA and/or DTSC hazardous waste limits when analyzed for leachability and be required to be disposed of in a RCRA Class I landfill. Characterization of Site material for disposal will be governed by receiving facility requirements, such as the number and type of samples per a volume unit, and leachate testing procedures such as the California Waste Extraction Test (WET) and the federal Toxicity Characteristic Leachate Procedure (TCLP).

Based on the time the lead-containing material has been exposed at the Site, it was assumed that Site material will be disposed of at a Class II landfill. The nearest cost effective RCRA Class II Landfill is Waste Management’s McKittrick facility west of Bakersfield, California. If waste classification results indicate that Site material requires Class I landfill disposal, the cost implications will need to be evaluated.

Excavation and offsite disposal is the most direct and efficient method of reducing contaminant concentrations, immediately provides maximum protection to the environment, complies with ARARs, and is cost effective and is the selected remedy per the Action Memorandum (NPS, 2018).

5 REMOVAL ACTION IMPLEMENTATION

5.1 Site Visit and Coordination

Prior to excavation, the Contractor will conduct a pre-construction Site visit with the NPS. The Contractor will complete and perform all notifications, permits, and compliance requirements to ensure a safe removal project. The excavation area will be demarcated as a safe work zone, including delineation of utility clearances. Figure 4 shows the estimated COEC impact area based on the EE/CA site investigation and confirmed during ECM’s site visit. Figure 3 shows the exposed bedrock, construction materials staging areas, and the approximate burn pit outline. The Contractor will coordinate with NPS, the Grant Grove Stable concessionaire, local Park air program, and state officials on all necessary activities. The Contractor will confine operations within the limits put forward in this document and the former EE/CA to prevent damage to natural surroundings.

5.2 Waste Characterization and Disposal Plan

5.2.1 Extent of Contamination Sampling

The full extent to which COECs associated with the Site may have migrated within the soil has not yet been determined. Therefore, the Contactor will perform in-process characterization screening using an XRF analyzer to determine the lateral and vertical extent of metals contamination within the two refuse areas shown on Figure 7 during excavation. The two debris areas shown on Figure 7 were identified visually during the EE/CA and SI and will be identified in the same manner during the removal action. Section 5.2.1.2 below details the procedure for XRF screening sampling and quality control.

The Contractor will complete step-out XRF readings 25 feet in a downgradient direction from each existing sample location that exceeds RGs as shown on Figures 6 and considering refuse and debris boundaries shown on Figure 7. Samples with one or more COEC that exceed RGs include GG-SO-05 through GG-SO-08 on Figure 6. Results will be recorded for XRF readings for only those metals that are COECs. The step-out readings will help define the excavation boundary prior to removal of materials. COECs include cadmium, chromium, copper, lead, mercury, vanadium, and zinc. 2,3,7,8-TCDD TEQ is also listed as a COEC in the EE/CA but cannot be analyzed with an XRF. Based on results of the EE/CA sampling, it is assumed that the presence of 2,3,7,8-TCDD TEQ would be present in locations where metals COECs are also present. Confirmation samples sent to the laboratory for analysis will include all COECs.

The contractor will continue stepping outward in 25-foot increments until all COECs are confirmed below their respective RGs.

Once visual observation of waste materials and XRF screening readings for cadmium, chromium, copper, lead, mercury, vanadium, and zinc in the step-out samples are recorded below the RGs for all COCs, the bounds of the excavations will be set. The Contractor will use a global positioning system (GPS) unit to record the location of each XRF sample, along with the bounds of each final excavation area. Wooden stakes or flagging will be used along the perimeter of the excavation area to indicate the extent of the excavation.

The extent of excavation will initially be based on visual observations of refuse and debris removal and will be confirmed with XRF and laboratory confirmation samples as described in Section 5.2.3. Professional judgment will be used to determine if minimal stray surface refuse beyond the extent of XRF delineation requires expansion of the excavation extents.

All data will be reviewed and summarized by an Environmental Professional for NPS approval prior to backfill operations.

5.2.1.1 Field Documentation

The Contractor field personnel will document all XRF readings and soil samples from the excavation area. Sample locations, XRF results, sample labels, collection time, , and chain of custody (C-O-C) documents will be completed and included in the closeout report. Additionally, digital photos will be taken of the Site prior to any ground disturbing activities, as well as throughout the excavation work, including sample locations. Post-excavation photos will be collected to document final conditions before departing the Site. The Contractor will produce a comprehensive photographic log.

5.2.1.2 XRF Sampling and Quality Control Procedure

XRF analysis requires dry conditions; soils must contain 20 percent or less moisture by volume for accurate measurements. Samples containing greater than 20 percent moisture must be dried prior to XRF analysis. Prior to the start of XRF monitoring each day and once in the middle of the day (twice per day), the Contractor will analyze a blank and known standard with the XRF. The resulting data from a blank should contain no or trace amounts of the elements of interest. The standard includes known concentrations of elements. XRF readings taken of the known standard will be compared against the known contents of the standard to note the accuracy and precision of the XRF results. Analyzing a standard prior to beginning analysis is essential because it confirms that the XRF instrument is functioning to specifications and producing accurate results. Results for the analysis of standards throughout the field effort will be logged and compared against the certified values of the standard for each relevant COEC.

Standard checks will be reported in a quality control summary table in the Removal Action Completion Report (RACR). In addition, the XRF supplier will ensure that the XRF has been properly calibrated within the past twelve months and the calibration certification will be provided in the RACR. If possible, the Contractor will obtain the XRF with the most recent calibration record.

Surface detritus, organic material, debris, and large gravel (>1/4 inch), if present, will be cleared away from each sample location to reveal solid media. Disturbance of solid media should be minimized to collect a representative sample. The XRF probe window will be positioned in direct contact with the soil surface to be analyzed. Sample analysis will then be initiated by depressing the XRF trigger and exposing the sample to primary radiation from the source for at least one minute, ensuring that the XRF unit is programmed to record each of the COCs. The XRF will be used to determine when subsurface native soil has been reached below the waste materials during excavation.

X-rays from the sample enter through the detector window and are converted into electric pulses in the detector. The longer the X-ray exposure during each XRF reading, the lower the level of detection will be and the more accurate the sample results will be. The Contractor should test the XRF in the field and adjust the exposure time as necessary to give a level of detection that is lower than the RGs for each COEC.

5.2.2 Excavation Plan

The following sections provide procedures to complete excavation activities at the Site.

5.2.2.1 Mobilization and Housekeeping

The Contractor will mobilize equipment, materials, and personnel to complete the excavations.

Excavation activities will be performed during the dry part of the year, approximately June to September.

Excavation activities will be performed during the dry part of the year. Excavation of contaminated soils will not be conducted during severe weather conditions (i.e., heavy rain and/or high winds). Avoiding excavation during precipitation events will eliminate the potential for storm runoff and erosion at the Site. Hours of construction will be limited to 7 a.m. to 6 p.m., Monday through Friday. All field activities at the Site shall be conducted under the supervision of a California-licensed Professional Engineer (P.E.) or Professional Geologist (P.G.). The Contractor will incorporate decontamination methods for all vehicles, haul trucks, and construction equipment used at the Site. All vehicles entering SEKI shall be clean and free of soil that could contain invasive seeds or other contaminants. Every day, prior to commencement of work, all equipment will be inspected for leaks and repaired immediately, if needed.

Equipment that is leaking will not be used and will be removed from the Site. Absorbent materials will be available at the job site in the event of spills. The Contractor will install barrier tape where directed by NPS Park staff. The Contractor will always have a minimum of two rolls of barrier tape onsite.

The Contractor field supervisor must be capable and qualified to be in charge of fire protection.

All Contractor employees working on site must be HAZWOPER qualified per Occupational Safety and Health Administration 29 Code of Federal Regulations (CFR) Part 1910.120(h) with current certification. Site sampling personnel must be qualified and experienced in U.S.

Environmental Protection Agency (EPA) methods and sampling protocols for modified EPA Method 6200 analysis and Interstate Technology & Regulatory Council (ITRC) requirements for ISM sampling.

5.2.2.2 Excavation and Demarcation

Once mobilized to the Site, the Contractor will provide temporary barriers to protect existing trees, plants, and root zones within the work area. Brush will be cleared to expose soils within the excavation area as approved by NPS personnel. The Contractor will not remove, injure, or destroy trees or other plants without prior approval. There are several large pines and cedars within the removal area that will be protected during the removal action. The tree protection zone (TPZ) radius in feet will be equal to the diameter of the tree in inches measured at chest height. For example, a 24-inch diameter tree requires and 24-foot TPZ radius. The TPZ for each tree will be demarcated with marking paint or demarcation flagging, and no ground disturbance will be allowed to occur withing the TPZ without approval by NPS biologists. The TPZ calculation is based on reference provided by NPS, Best Management Practices: Managing Trees During Construction (Fite, 2016).

There are also rare plant species documented near the Site. If any rare plant species are to be protected during the removal action, NPS biologists will demarcate the plant(s) with flagging.

The Contractor will notify the Park Representative and utility companies of proposed locations and times for excavation. The Contractor will complete a USA dig alert prior to excavation. The Contractor will be responsible for locating and preventing damage to known utilities.

5.2.2.3 Soil Excavation

Excavation and off-Site disposal involves the removal of the contaminated materials, waste characterization, transportation, and subsequent disposal at an appropriately permitted facility.

The type of facility is dependent on the class and concentration of hazardous materials in the waste. Wastes found to exceed state or federal guidelines for hazardous waste must be transported to a RCRA landfill for disposal. All excavated wastes will be managed in accordance with all applicable federal, state, and local requirements. NPS requires that the contractor obtain NPS approval of the disposal locations and hauling contractor prior to commencement of work.

Excavation of waste materials is expected to occur in two principal areas shown on Figures 4 and 7. The two areas are divided by exposed bedrock on the northwestern corned or the staging/burn pit area of the Site. The northwest excavation area includes seismic line SL-1 while the western area includes seismic lines SL-2 and SL-3.

Extent of excavation will initially be based on visual observation of debris removal and will be confirmed with XRF, and laboratory confirmation samples as described in Section 5.2.3.

The flat area of the Site labeled Burn Pit on Figure 3 contains stockpiled clean materials that would be relocated and stored for later use prior to excavation. This area will be used for stockpiling excavated materials and for staging equipment. Material from the refuse area and debris field will be removed in 6-inch lifts until visual observation indicates that the waste material has been removed and XRF results confirm that RGs have been met.

5.2.2.4 Soil Stockpiling

The excavated soils will be placed into two staging piles on Site in a location near, but not blocking, the site access road. The Contractor will segregate excavated materials based on level of contamination, with one stockpile for soils suspected to exhibit lower concentrations of COCs and one stockpile more likely to contain elevated COCs. The Contractor will use visual inspections, data results included on tables and figures within this document, and real-time XRF readings to segregate materials. All impacted soil will be placed in approved roll-off boxes or stockpiled on thick plastic sheeting, and immediately covered for protection from the elements (wind and/or rain) with similar plastic sheeting for temporary storage prior to transport and disposal at a licensed facility. NPS is currently storing wood chips at the recommended staging area. Depending on the amount stored at the Site at the time of the removal action, the wood chips may need to be consolidated and moved by the contractor with approval from NPS. A pre-work site visit should be completed to assess the soil stockpile location.

5.2.3 Excavation Extent and Confirmation Sampling

Once soil is excavated to the extent that visual observation confirms the removal of waste debris in soils, the contractor will use the XRF meter to screen the soil for metals in the excavation bottom and side walls and confirm that residual metal concentrations are below the EE/CA RGs prior finishing excavation and collecting confirmation ISM soil samples. The XRF analyzer will aid the field sampling effort and reduce the need for over-excavation of soil. If RG exceedances are detected with the XRF meter, additional soils will be removed until RGs are met.

Once all excavation floor and sidewall XRF readings for metals meet the RGs shown in Table 1 above, laboratory samples will be collected using ISM sampling techniques on the excavation floor and sidewalls. Laboratory samples will be analyzed for cadmium, chromium, copper, lead, mercury, vanadium, and zinc using EPA Method 6010B and 3,7,8-TCDD TEQ using EPA Method 1613 at a California-certified laboratory to confirm that concentrations meet the RGs shown in Table 1. Laboratory samples must be prepared using ISM protocols prior to analysis.

The Contractor must develop a confirmation Sampling and Analysis Plan (SAP) using ISM sampling techniques to be approved by NPS prior to beginning the removal action. Each ISM sample consists of 30 equal volume increments collected in a representative manner over the subject area. Triplicate ISM samples will be collected from excavation floors and walls. The two refuse areas are each approximately 0.5 acres. It is anticipated that each refuse area will require 6 ISM samples (2 locations, 3 samples each) for a total of 12 ISM samples from the two refuse areas. The two debris fields are somewhat larger, but the ultimate extent of the excavation is less certain than in the refuse areas. It is anticipated that the northern debris areas will require 6 ISM samples and the western debris field will require 12 ISM samples (4 locations, 3 samples each) for a total of 18 ISM samples from the debris areas. These anticipated numbers of samples like represent the maximum number of samples required.

Enough sample volume must be collected from each of the 30 equal volume increments as recommended by the ITRC Section 4 Field Implementation. Increments will be collected from 0-6 inches below ground surface (bgs) using a disposable hand trowel. Trowels will be dedicated to each replicate; one trowel may be used to collect each of the 30 increments per replicate but must be decontaminated or disposed of between replicate samples. Enough volume must be collected to meet the laboratory volume required for ISM samples (approximately 1 kg per ISM sample) and the entire volume must be sent to the laboratory. The selected laboratory must have SOPs specific to ISM samples. The composite samples will be collected in one-gallon Ziplock bags and transported on ice under C-O-C to Test American or another NPS-approved, California-certified laboratory. Samples will be prepared by the laboratory following ISM protocol for sample processing and analysis per ITRC Section 5 Sample Processing and Analysis (ITRC, 2020).

Results of the confirmation sampling must show that the Site meets RGs prior to backfill and Site restoration. If results for the confirmation sampling do not meet the RGs, additional excavation and confirmation sampling would be required. The Contractor will prepare a technical memorandum presenting the confirmation sampling results to NPS prior to initiating any backfill and site restoration activities. Results should be provided to NPS within 10-days of receipt to ensure that soils are not stockpiled on site for longer than necessary.

5.2.4 Waste Characterization of Stockpile

Once soil is excavated to the extent of contamination defined by the XRF step-out screening and confirmatory sampling has been completed on the excavation floor and sidewalls, the excavated soil stockpiles will be evaluated.

Samples are necessary for use in waste designation and identification of treatment requirements. Three five-point composite samples will be collected from each stockpile for laboratory analysis. Composite subsamples will be collected from each stockpile, such that the composite sample for each staging pile represents the entire staging pile. The composite sample will be homogenized to ensure even distribution of each subsample. The composite sample will be placed into laboratory supplied glassware and transported to the laboratory under C-O-C procedures.

The EE/CA cost estimate assumes the soil within each staging pile will not be designated as hazardous waste, will be classified as Class-II non-hazardous soil, and therefore will not require treatment prior to off-site disposal. Analysis of the composite samples will be run in triplicate for total metals by EPA Method 6010B, EPA’s TCLP, EPA’s Soluble Threshold Limit Concentration (STLC), EPA’s Total Threshold Limit Concentration (TTLC), and the WET.

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